Unmanned security doors allow access to restricted areas by receiving from a user input commands for requesting access to the secured area. Such access is requested by several means, including a magnetic card having a magnetic strip that is passed over a magnetic reader for reading an identification access code encoded on the magnetic strip. A remote access requester receives the user-supplied commands and provides such commands to a controller that is typically located a distance from the remote access requester. Communication between the remote access requester and the controller is typically over a multiple conductor transmission line. If the user of the facility having a security systems desires to change such system, the user may need to install a multiple conductor transmission line, which can be costly.
Many security systems use a Wiegand standard interface for communicating data signals from the remote access requester and the controller. The Wiegand standard has five-conductor transmission lines for communicating power, ground, a lamp indicator signal, and two data lines for a one pulse and a zero pulse. Consequently, using a remote access requester and a controller implemented with the Wiegand standard cannot be used on a two-conductor transmission line infrastructure.